In the prior art, a PCT publication WO9636163 discloses steganography systems. The improvements include facilitating scale and rotation registration for steganographic decoding by use of rotationally symmetric steganographically embedded patterns and subliminal digital graticules; improved techniques for decoding without access to unencoded originals; improving robustness of steganographic coding in motion pictures and/or in the presence of lossy compression/decompression; and representing data by patterned bit cells whose energy in the spatial domain facilitates decoding registration. Applications include enhanced-security financial transactions, counterfeit resistant identification cards, fraud deterrent systems for cellular telephony, covert modem channels in video transmission, photo duplication kiosks with automatic copyright detection, and hot linked image objects (e.g. with embedded URLs) for use on the Internet.
It is further known to encrypt an image in order to prevent the image being recognized or to prevent its contents being read by unauthorized persons. One technique of encrypting an image is disclosed in, for example, European Patent Application EP 0 260 815. This technique, also known as visual cryptography, employs two patterns or“shares”, each of which cannot be recognized individually, which are overlaid to produce a recognizable image. To this end, the original image is transformed into two randomized image patterns, neither of which contains any perceptible image information. One of these patterns is printed on a transparency to act as a key. When such patterns are overlaid, the patterns are combined and thus“decrypted” in the eye of the viewer.
Rather than working with transparencies which are cumbersome when larger amounts of individually encrypted images are to be viewed, it has been proposed to use a decrypting (decryption) device. Two types of image decrypting devices can be distinguished: transparent and non-transparent devices. Transparent decrypting devices essentially mimic the transparent sheets used in the Prior Art and display one pattern (“share”) of the encrypted image. As the decrypting device is at least partially transparent, the other pattern of the image can be seen through the device and the two image patterns are combined in the eye of the viewer as before.
Further in the prior art steganographic methods currently known generally involve fully deterministic or “exact” prescriptions for passing a message. Another way to say this is that it is a basic assumption that for a given message to be passed correctly in its entirety, the receiver of the information needs to receive the exact digital data file sent by the sender, tolerating no bit errors or “loss” of data. By definition, “lossy” compression and decompression on empirical signals defeat such steganographic methods. (Prior art, such as the previously noted Komatsu work, are the exceptions here.)
The principles of this technology can also be utilized as an exact form of steganography proper. It is suggested that such exact forms of steganography, whether those of prior art or those of this technology, be combined with the relatively recent art of the “digital signature” and/or the DSS (digital signature standard) in such a way that a receiver of a given empirical data file can first verify that not one single bit of information has been altered in the received file, and thus verify that the contained exact steganographic message has not been altered. The simplest way to use the principles of this technology in an exact steganographic system is to utilize the previously discussed “designed” master noise scheme wherein the master snowy code is not allowed to contain zeros. Both a sender and a receiver of information would need access to both the master snowy code signal and the original unencoded original signal. The receiver of the encoded signal merely subtracts the original signal giving the difference signal and the techniques of simple polarity checking between the difference signal and the master snowy code signal, data sample to data sample, producing a the passed message a single bit at a time. Presumably data samples with values near the “rails” of the grey value range would be skipped (such as the values 0, 1, 254 and 255 in 8-bit depth empirical data).
The need for the receiver of a steganographic embedded data file to have access to the original signal can be removed by turning to what the inventor refers to as “statistical steganography.” In this approach, the methods of this technology are applied as simple a priori rules governing the reading of an empirical data set searching for an embedded message. This method also could make good use of it combination with prior art methods of verifying the integrity of a data file, such as with the DSS. (See, e.g., Walton, “Image Authentication for a Slippery New Age,” Dr. Dobb's Journal, April, 1995, p. 18 for methods of verifying the sample-by-sample, bit-by-bit, integrity of a digital image.)
Statistical steganography posits that a sender and receiver both have access to the same mastersnowy code signal. This signal can be entirely random and securely transmitted to both parties, or generated by a shared and securely transmitted lower order key which generates a larger quasi-random master snowy code signal. It is a priori defined that 16 bit chunks of a message will be passed within contiguous 1024 sample blocks of empirical data, and that the receiver will use dot product decoding methods as outlined in this disclosure. The sender of the information pre-checks that the dot product approach indeed produces the accurate 16 bit values (that is, the sender pre-checks that the cross-talk between the carrier image and the message signal is not such that the dot product operation will produce an unwanted inversion of any of the 16 bits). Some fixed numbers of 1024 sample blocks are transmitted and the same number times 16 bits of message is therefore transmitted. DSS techniques can be used to verify the integrity of a message when the transmitted data is known to only exist in digital form, whereas internal checksum and error correcting codes can be transmitted in situations where the data may be subject to change and transformation in its transmission. In this latter case, it is best to have longer blocks of samples for any given message content size (such as 10K samples for a 16 bit message chunk, purely as an example).
The images used for synchronization purposes may show an identification token, such as a number, letter or name, to allow an easy recognition of the correctly decrypted image. This token could identify a key on the display device which could be pressed to identify the correctly decrypted image.
Although various ways of receiving user input can be envisaged, it is preferred that the display device receives the user indication via a pointing device and/or a keyboard. A suitable pointing device is a so-called mouse, although other pointing devices, such as a “track ball” or a “touch-pad mouse” can also be used. The term “keyboard” as used here is meant to include other key arrangements, such as keypads. Alternatively, the use of touch-screen technology may be advantageous.
The images used for synchronization according to the present invention may be monochrome images or color images although various techniques may be used for rendering color images in visual cryptography and similar applications.
At present, all QR codes generated and used by manufacturers are basic in nature and contain basic data such as URL codes or product information. Security is a big concern with QR codes at the moment. The biggest worry is that consumers scanning QR codes can easily be hijacked into malicious web sites, instead of original, intended web sites of manufacturers. The QR codes at present can't be used for shopping, buying or authentication purposes.